As a prior technology regarding a current detector of a magnetic proportional type, an example is disclosed in Patent Literature 1. A current detector of a fifth embodiment of Patent Literature 1 is described with reference to FIG. 21. FIG. 21 is a perspective view illustrating the current sensor of the fifth embodiment of Patent Literature 1 in an exploded manner.
A current detector 90 of the fifth embodiment of Patent Literature 1 includes a resin case 92. In the resin case 92, plate-shaped sheet cores 94 and 96 are accommodated as being stacked in plural. These sheet cores 94 and 96 configure one magnetic core 98 as being accommodated in the resin case 92. While two sheet cores 94 and two sheet cores 96 are illustrated in FIG. 21, the actual number of sheets is more, illustration of which are omitted in the drawing.
The sheet cores 94 and 96 are each formed in a substantially-angular C shape, and the above-shaped sheet cores 94 and 96 are formed by punching a plate-shaped magnetic material. Here, the sheet cores 94 and 96 have openings 94a and 96a, respectively, at the center position, and gap-purpose slits 94b and 96b extending from the openings 94a and 96a, respectively, are formed toward one side edge. The openings 94a and 96a are each formed in a substantially square shape, matching the outer shape of each of the sheet cores 94 and 96, respectively.
When the sheet cores 94 and 96 are accommodated as being stacked inside the resin case 92, the openings 94a and 96a and the gap-purpose slits 94b and 96b mutually match each other when viewed in a stacking direction. Thus, with many sheet cores 94 and 96 configuring one magnetic core 98, a successive through hole is formed at the center position, and a core gap is formed in part of the circumferential direction.
Inside the resin case 92, an accommodating part 92a and a guide sleeve 92b are formed. The accommodating part 92a has an upper portion illustrated in FIG. 21 open and a bottom plate 92c formed therebelow. The guide sleeve 92b extends upward from above the bottom plate 92c, and has its inside formed as a hollow current conductive part 92d. The outer shape of the guide sleeve 92b is slightly smaller than each of the openings 94a and 96a of the sheet cores 94 and 96, and the dimensions inside the accommodating part 92a are larger than the outer shape of each of the sheet cores 94 and 96. Therefore, when the sheet cores 94 and 96 are accommodated inside the resin case 92, each of the openings 94a and 96a is guided along the outer surface of the guide sleeve 92b, thereby making it easy to position the sheet cores 94 and 96 mutually.
Inside the resin case 92, together with the sheet cores 94 and 96, a Hall element 10 is also accommodated. The Hall element 10 is mounted on a circuit board 12, and the circuit board 12 is accommodated so as to be stacked on the upper surface of the sheet core 96 of the outermost layer. Here, the Hall element 10 is inserted through the gap-purpose slits 94b and 96b of the sheet cores 94 and 96, thereby being positioned inside the core gap of the magnetic core 98.
In the fifth embodiment, one sheet core 94 is made of an iron-nickel alloy (for example, PB=45% Permalloy and PC=78% Permalloy) as a material, and the other sheet core 96 is made of a non-oriented silicon steel plate as a material.
In this case, the sheet core 96 is made of a non-oriented silicon steel plate, and has a portion with degraded magnetic characteristics as a core for current detection (in particular, hysteresis width). However, the other sheet core 94 is made of Permalloy, and has excellent magnetic characteristics (output linearity, hysteresis width, and saturation characteristics) as a core for current detection. By stacking these sheet cores 94 and 96 of different magnetic materials to configure the magnetic core 98, a defect unique to the sheet core 96 can be compensated for by another sheet core 94. As a result, favorable magnetic characteristics can be achieved in the magnetic core 98 as a whole, and characteristics sufficient as a product can be achieved.
Also in the fifth embodiment, since the non-oriented silicon steel plate of a relatively inexpensive magnetic material and Permalloy of a relatively expensive magnetic material are used in combination, the amount of use of Permalloy with respect to the whole can be suppressed, and it is possible to contribute to saving of material cost accordingly.